Cultivated crops in the plant family Cucurbitaceae such as watermelon, squash, cucumber and melon have been using grafted plants for commercial production in many production areas. This is done to overcome problems related to soil borne pathogens, abiotic stress and for improvement in yield and fruit quality, and for extension of the growing season. Consequently, there is a strong demand in many parts of the world for grafted cucurbit plants, including Asia, Europe, the United States of America and Mexico. However, grafting cucurbits is a labor intensive process which requires a skilled, efficient, and consistent labor force. The cost and quality of grafted plants are key input cost for production.
Typically, the rootstock varieties (Lagenaria spp., interspecific squash hybrids, wax gourds or wild watermelon) used in grafting produce much more vigorous plants than scion plants, and thus the shoot growth of the rootstock on grafted plant can outcompete the scion for light, water and nutrients. Consequently, the standard practice is to remove by hand the shoot tip of rootstock in the seedling tray before grafting and again before grafts leave the transplant house. The grower then needs to scout fields and further hand prune rootstock shoot growth in the field for a period of time to eliminate any shoots of the rootstock plants that were missed or have regrown. Failure to remove rootstock shoots can adversely affect the development of grafts in transplant production, the establishment of grafted plants in the field, and the productivity of grafted plants due to the competition by the vigorous rootstock shoots that remain and are allowed to grow.
This repeated pruning can represent a significant labor need and expense to the grower and is particularly limiting in areas where labor costs are high, such as in the U.S. Currently, in Mexico, growers are able to commercially supply grafted watermelon plants, but in the U.S., grafted cucurbit plants are not produced on a commercial scale. Phytosanitary import restrictions prevent the movement of soil (or seedlings in soil) from Mexico to the USA, therefore, the U.S. commercial production cannot easily use grafted plants produced in Mexico.
The present invention overcomes the shortcomings in the field by providing alternative methods for inhibiting the shoot apical meristem of a cucurbit rootstock plant to be used in grafting procedures.